Caramel colors are colorants widely used in food and beverages. Ranging in color from pale-yellow to dark-brown, caramel colors are prepared commercially from food grade nutritive carbohydrate sweeteners (glucose and fructose and/or polymers thereof, e.g., sugar, corn-syrup and starch hydrolyzates) by controlled heating of these materials to generate desired degrees of unsaturation, polymerization and color.
An identity scheme proposed by the International Technical Caramel Association (ITCA) classifies caramel colors according to four general “Classes,” based on their method of manufacture, composition, functional properties and applications. Ten specific “Types” are also identified, based upon their color intensity.
In caramel colors that utilize ammonia as a reactant, 4-methyl-imidazole (4-MeI) is produced. It is generally preferable, however, to form as little 4-MeI as possible.
U.S. Patent Application Publication No. 2010/0003383 (Parker et al.) describes a method of making a low-4-MeI caramel by reacting a carbohydrate with ammonium bisulfite and water at an initial pH of less than 5. The reactant mixture of carbohydrate, ammonium bisulfite, acid and water is then heated in a closed vessel to a temperature and for a time sufficient to initiate the caramel reaction. The rate of the reaction is then controlled by subsequently adding base in a controlled manner to maintain a desired low pH. However, the caramels produced by this method have unusual gelling properties, rendering such caramels unsuitable for commercial use.
U.S. Pat. No. 4,416,700 describes caramel color concentrates prepared by subjecting a mixture of caramel color and water to ultrafiltration through a semi-permeable membrane, wherein the pH and/or ionic strength of the caramel color/water mixture, at all or particular stages of the ultrafiltration process, is regulated so as to obtain desirable processing and product attributes, such as increased removal of low molecular weight materials.
U.S. Pat. No. 5,114,492 relates to the separation of color solids from caramelized carbohydrate solutions by the use of ultrafiltration, and more particularly, to a continuous process for separation of these solids into a color fraction and a non-color fraction with recycle of the non-color fraction to produce color bodies having an acceptable flavor for use in beverages or food. In particular, the '492 patent discloses a molecular weight cut off (MWCO) of at least about 10,000 Daltons and higher.
There remains a need for novel methods of producing stable, i.e., non-gelling, low-4-MeI, class IV caramels. There also remains a need for novel methods of reducing low molecular weight species in caramels, more generally.